Persistent, bioaccumulative, and toxic pollutants in migratory waterbirds from Bohai Bay, China: Implications on distinct pollutant sources.

Bohai Bay is an important stopover on the East Asian-Australasian flyway (EAAF) for migratory birds. In the present study, eggs of three migratory waterbird species, Little Terns (Sterna albifrons), Pied Avocets (Recurvirostra avosetta), and Black-winged Stilts (Himantopus himantopus), and local aquatic organisms from Bohai Bay (Nanpu and Dongying wetlands) were collected to determine stable isotope (C, N, D) signature and concentrations of mercury (Hg), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), and short-chain chlorinated paraffins (SCCPs). Organisms from Nanpu had significantly higher δD values than Dongying, which was related to local salinity. The pollution profiles showed species-specific difference in the same site, but no spatial difference for the same bird species from two wetlands. Positive correlations were observed between δN values and concentrations of Hg and PCBs, but not DDTs and SCCPs, because of the complex pollution sources in migration routes. The pollution exposure in the annual life cycle for Pied Avocets based on migration route information suggests that Hg and PCBs in eggs mainly originate from the breeding site (Bohai Bay), while DDTs are mainly from the wintering sites (the middle and lower reaches of the Yangtze River). Pollutants could pose considerable negative effect on eggshell thickness. The present study promotes the importance of pollutant exposure and risk assessment in the entire migration cycle for migratory birds.